What are disinfectants and sanitizers?

Definition

Disinfectants and sanitizers are antimicrobials. A “disinfectant” destroys pathogens (disease-causing microorganisms, such as
bacteria) but not spores and not all viruses. A “sanitizer”
reduces the number of harmful microorganisms, or germs, so that they are not an
infectious hazard. Disinfection and sanitization are effective only if a surface
area is clean. “Clean” means that a surface has been cleared of soil, dust,
organic matter (such as blood or stool), and microorganisms. Cleaning usually can
remove large amounts of harmful microorganisms, but it usually does not kill them
and does not disinfect or sanitize surfaces.

According to industry standards, a disinfectant must be capable of reducing the level of pathogenic bacteria by 99.999 percent during a time frame greater than five but less than ten minutes under conditions of the AOAC Use-Dilution Test. A disinfectant destroys all pathogens on a surface or object. Disinfectant products or processes can be ranked as low, medium, or high level. A sanitizer must reduce the level of harmful microorganisms by in a specific bacterial test population 99.999 percent (in a process known as a 5 log reduction) within thirty seconds under conditions of the AOAC Germicidal and Detergent Sanitizers Test (GDS).

One substance may work both as a sanitizer and a disinfectant. For example, an iodophor, when used at 25 ppm (parts per million of available iodine), is a sanitizer. However, that same product, when applied at 75 ppm, is a disinfectant. After using the sanitizer, which kills 99.999 percent of bacteria, five thousand bacteria per square foot would remain. These remaining microorganisms reproduce by splitting into two every fifteen minutes. The result is that those five thousand bacteria per square foot have now become 1 million bacteria per square foot within, for example, five hours.

The U.S. Environmental Protection Agency (EPA) is the governing body
for antimicrobials. It places antimicrobials into four categories: sterilizers,
disinfectants, sanitizers, and antiseptics and germicides. A sterilizer is
equipment used in medical procedures. Cleaning professionals are concerned only
with disinfectants and sanitizers, which are chemical antimicrobial agents, in
contrast to physical antimicrobial agents, such as heat and radiation. Antiseptics and germicides are for use on living beings and are
governed by the U.S. Food and Drug Administration (FDA). A sanitizer may be called an antiseptic when it is used on tissue.
(Antiseptics are safe to use in this case because they do not have the same
killing power as disinfectants.)

Development of Sanitizers and Disinfectants

Infection control was pioneered by hospitals in the nineteenth century. Out of the filth, disease, and poverty of the early nineteenth century came sanitary reform. One of the more significant contributors to the health revolution was the technological, sociological, and environmental phenomenon now known as the sanitary era or the public health campaign. The goal of this campaign was to destroy all possible harmful microorganisms.

Health officials believed it was practical to allow a minimum of ten minutes of contact time with a sanitizer or disinfectant to accomplish this objective. As a result, most disinfectant tests were developed to ascertain whether any bacteria could survive exactly ten minutes of contact. When contact times that are significantly less than ten minutes are allowed, it becomes difficult to get a meaningful result from the Use-Dilution Test.

In food service and public-health related industries, interest in antimicrobials appeared much later than it did in hospitals. Conditions of use were different, so tests based on ten minutes of contact were not practical. In many cases even today, thirty seconds is about the maximum time one can realistically expect for contact in food and drink service (such as when a bartender washes a glass).

Because it is not realistic to expect complete kill in thirty seconds, the GDS test was developed to count microbes. (The Use-Dilution Test, in contrast, indicates the presence of bacteria but yields no counts.) Experts figured that it was possible to get, in thirty seconds, a 99.999 percent reduction in the amount of bacteria with the use of practical agents (such as detergents).

Common Mechanism of Action

A wide range of substances are used as disinfectants. These include alcohols, aldehydes, hydrogen peroxide, iodine, and potassium permanganate solution. Bromine and chlorine are the most common disinfectants and sanitizers for drinking and recreational waters.

The most widely used disinfectants and sanitizers are powerful oxidizers, which means that the atoms of these elements can accept
electrons or hydrogens, or both. Hydrogen peroxide, bromine, and chlorine
compounds oxidize the complex molecules present on the surface of bacteria,
causing their cell walls and cell membranes to disrupt. The proteins on the
surface become irreversibly damaged and start to stick together, forming clumps.
This happens quickly: A strong solution of sodium hypochlorite (NaOCl, also known
as household bleach) solution that is used to disinfect a toilet, for example,
kills bacteria within seconds. The bacterial cell cannot respond to the damage
quickly enough, and the whole cell simply splits open and dies.

Later research has shown that bacteria do have some capacity to resist an attack by bleach. Contact with hypochlorous acid was found to switch on a gene in some bacteria. This gene is part of the pathway that bugs use to cope with heat stress and the bleachlike substances that cells of the immune system produce to fight infection. If the concentration of bleach solution is low, bacteria with genes that resist this sort of cellular attack might survive.

Impact

It has been claimed that the major decline in mortality in the late nineteenth and early twentieth centuries resulted from innovations in environmental sanitation. About one century later, in 1997, Life magazine considered drinking water chlorination and filtration to be “probably the most significant public health advancement[s] of the millennium.”

Today, modern hospital disinfectants must show efficacy in eliminating three primary organisms: Staphylococcus aureus, Salmonella, and Pseudomonas aeruginosa. However, hospital administrations generally require disinfectants with even more efficacy.

Many people in developed countries have grown to accept reduced rates of
illness as the norm, and outbreaks that once would have been accepted as an
unavoidable part of life are now considered crises of public health that require
swift and decisive interventions. However, much of the developing world has yet to
reap the benefits. According to World Health Organization (WHO) data,
worldwide, two of every ten people live with no source of safe drinking water and
four of every ten people lack access to a simple pit latrine.

There remains more work to be done. WHO has promoted as one of its Millennium Development Goals the reduction by one-half, by the year 2015, of the proportion of people without sustainable access to safe drinking water and basic sanitation. Efficacious and inexpensive, chlorine disinfectants have been employed to help achieve this critical humanitarian goal.

Bibliography

Block, Seymour S., ed. Disinfection, Sterilization, and Preservation. 5th ed. Philadelphia: Lippincott Williams & Wilkins, 2001. A comprehensive and practical reference on contemporary methods of disinfection, sterilization, and preservation and their medical, surgical, and public health applications.

Fraise, Adam P., Peter A. Lambert, and J.-Y. Maillard, eds. Russell, Hugo, and Ayliffe’s Principles and Practice of Disinfection, Preservation, and Sterilization. Malden, Mass.: Wiley-Blackwell, 2004. A highly respected established text covering in detail many methods to prevent and eliminate microbial growth.

Novick, Lloyd F., Cynthia B. Morrow, and Glen P. Mays, eds. Public Health Administration: Principles for Population-Based Management. Sudbury, Mass.: Jones and Bartlett, 2008. The principles, practices, and skills essential to successful public health administration. Includes information on the Healthy People 2010 objectives and chapters on bioterrorism and emergency preparedness, public health systems research, and public health law.